Numerical Simulation And Experimental Study Of Gas-liquid Multiphase System In T-shaped Microchannels

Microfluidics is an emerging technology that has been developed in recent years.In the 1980 s,Micro-Electro-Mechanical Systems(MEMS)were proposed,and natural sciences began to develop in the direction of miniaturization and integration.The microchannel is the basic component of the microfluidic system,and the realization of the microfluidic system is accomplished under the superposition of microchannels of different structural dimensions.In this paper,the flow characteristics of gas-liquid two-phase flow and gas-liquid-liquid three-phase flow in microchannels are studied by experiments and numerical simulation.The results obtained can provide theoretical reference for the analytical design of microchannels.In the simulation of microchannel gas-liquid two-phase flow,CFD method was adopted.A meshing method for local mesh encryption is proposed,which can clearly capture the liquid film of Taylor flow in microchannel.At the same time,according to the simulation parameters of this paper,a new experimental device is designed.The following main conclusions were obtained: two-phase flow pattern in the gas-liquid microchannel was observed,the generation of the slug flow and the flow pattern conversion conditions were analyzed;the variation of liquid column and bubble length is basically the same;the change of the wall contact angle in the capillary does not Influence Taylor bubble formation,when the contact angle is between 0-90°,the length change is very small.When the contact angle is greater than 90°,the bubble generation period increases significantly;the capillary number increases from small to large,and the thickness of the liquid film gradually increases;the porosity in the channel increases with apparent gas phase velocity and decreases with liquid phase velocity.In the simulation of microchannel gas-liquid-liquid three-phase flow,the three-phase dispersion process of the liquid-gas-liquid and the two-stage fracture control law of the double emulsion were studied by establishing the double T-type microchannel physical model.By changing the operating conditions,such as flow rate and channel size,three-phase flow patterns of water/oil/air composite emulsion,bubbles and dispersed phase droplets alternately arranged,and a parallel liquid-liquid flow containing bubbles were obtained.The results showed that variety of flow rate contributed to the change of three-phase volume fraction,which further resulted in the change of flow pattern;channel inlet size made the Taylor bubble smaller,thereby affecting the three-phase flow pattern;three-phase flow is more complex and there are many flow patterns.In order to obtain regular droplets of emulsion,it is necessary to strictly control the channel conditions,fluid properties,etc.